Thin diamond foils are needed in many particle accelerator experiments regarding nuclear and atomic physics, as well as in some interdisciplinary research. Particularly, nanodiamond texture is attractive for this purpose as it possesses a unique combination of diamond properties such as high thermal conductivity, mechanical strength and high radiation hardness; therefore, it is a potential material for energetic ion beam stripper foils. At the ORNL Spallation Neutron Source (SNS), the installed set of foils must be able to survive a nominal five-month operation period, without the need for unscheduled costly shutdowns and repairs. Thus, a single nanodiamond foil about the size of a postage stamp is critical to the entire operation of SNS and similar sources in U.S. laboratories and around the world. We are investigating nanocrystalline, polycrystalline and their admixture films fabricated using a hot filament chemical vapor deposition (HFCVD) system for H- stripping to support the SNS at Oak Ridge National Laboratory. Here we discuss optimization of process variables such as substrate temperature, process gas ratio of H2/Ar/CH4, substrate to filament distance, filament temperature, carburization conditions, and filament geometry to achieve high purity diamond foils on patterned silicon substrates with manageable intrinsic and thermal stresses so that they can be released as free standing foils without curling. An in situ laser reflectance interferometry tool (LRI) is used for monitoring the growth characteristics of the diamond thin film materials. The optimization process has yielded free standing foils with no pinholes. The sp3/sp2 bonds are controlled to optimize electrical resistivity to reduce the possibility of surface charging of the foils. The integrated LRI and HFCVD process provides real time information on the growth of films and can quickly illustrate growth features and control over film thickness. The results are discussed in the light of development of nanodiamond foils that will be able to withstand a few MW proton beam and hopefully will be able to be used after possible future upgrades to the SNS to greater than a 3MW beam.

Organic composite materials can be readily found in our daily life, such as plywood used in construction industry and bamboo composites as indoor and outdoor flooring materials. These organic composite material systems consist of cellulose fibers bonded with each other through adhesives, leading to a bonded system with a gradient structure that possesses a unique structural behavior which has a great potential to be used as load-bearing building materials. In view of the manufacturing process of such composite material systems and the structure in-between the cellulose fibers and the adhesives, the interfacial adhesion of such systems at multiscale would play a major role in determining their capability in load-bearing structural applications. In this research work, the interface between cellulose fiber and phenol-formaldehyde adhesive is chosen as a representative of the organic composite material system and molecular dynamics simulation is used for quantifying their mechanical properties and the corresponding interfacial adhesion. Here we demonstrate that cellulose fiber has a strong affinity to a phenol-formaldehyde adhesive with an adhesion energy of 151.3 mJ/m2. To the best of our knowledge, this is the first study that reports this material property for cellulose-adhesive system, which is three times larger than that between the gecko foot’s hair and the mineral surface. The mechanism of such strong adhesion is due to the possible hydrogen bonding between the cellulose and the adhesive.

To prepare cholesteric liquid crystalline nonlinear optical materials with ability to be vitrified on cooling and form long time stability cholesteric glasses at room temperature, a series of platinum acetylide complexes modified with cholesterol has been synthesized. The materials synthesized have the formula trans-Pt(PR 3)(cholesterol (3 or 4)-ethynyl benzoate)(1-ethynyl-4-X-benzene), where R = Et, Bu or Oct and X = H, F, OCH 3 and CN. A cholesteric liquid crystal phase was observed in the complexes R = Et, and X = F, OCH 3 and CN but not in any of the other complexes. When X = CN, a cholesteric glass was observed at room temperature which remained stable up to 130 °C, then converted to a mixed crystalline/cholesteric phase and completely melted to an isotropic phase at 230 °C. When X = F or OCH 3 the complexes were crystalline at room temperature with conversion to the cholesteric phase upon heating to 190 and 230 °C, respectively. In the series X = CN, OCH 3 and F, the cholesteric pitch was determined to be 1.7, 3.4 and 9.0 µ, respectively.

Surface enhanced Raman scattering (SERS) is a sensitive and reproducible vibrational spectroscopic technique used to detect and characterize molecules near the surface of noble metals like Au, Ag, Pt, Cu, etc. SERS enhances Raman signals through light-induced plasmonic vibrations occurring on irregular metal surfaces and localized electromagnetic augmentation. To better define nano-scale regions of the Raman signal enhancement, we generated gold nanoparticles with a unique multi-branched configuration along with surface-adsorbed fluorescent reporter molecules. The reporter molecules included a set of near-infra red active fluorescent dyes IR820 (green cyanine, photo electronic dye), DTTC (3, 3'-diethylthiatricarbocyanine iodide) and DTDC (3, 3'- diethylthiadicarbocyanine iodide). We employed a one-pot synthesis method in order to generate a stellate configuration in gold nanoparticles through the reduction of HAuCl4 with Good’s buffer, HEPES, at pH 7.4 and room temperature. A cell viability assay was performed with normal esophageal cells exposed to the multi-branched gold nanoparticles and SERS molecules to assess their toxicity. Our results demonstrate the capacity of multibranched gold nanoparticles linked to Raman reporter molecules to generate distinct signature spectra and, with the exception of the gold nanoparticles functionalized with DTTC, remain non-toxic to normal esophageal cells.

Semi-insulating (SI) silicon carbide (SiC) was evaluated as a candidate material for dielectric substrate for patch antennas suitable for monolithic antenna integration on a SiC semiconductor chip. Computer simulations of the return loss were conducted to design microstrip patch antennas operating at 10 GHz. The antennas were fabricated using SI 4H-SiC substrates, with Ti-Pt-Au stacks for ground planes and patches. A good agreement between the experimental results and simulation was obtained. The radiation performance of the designed SiC based patch antennas was as good as that normally achieved from antennas fabricated using conventional RF materials such as FR4 and Rogers. The antennas had the gain around 2 dBi at 10 GHz, which is consistent with the conventional antennas of a similar size.

The Bastion of San Pedro is part of the defensive infrastructure projected by Spanish colonizers in San Francisco de Campeche City, in order to protect the city and their inhabitants from pirates who ravaged the region during the XVIth and XIXth centuries. The bastion is a masonry structure built by using calcareous materials according the Spanish procedures from the edge. Since its construction, it has been under the synergetic interaction of natural and anthropogenic factors that promote degradation. In this study optical microscopy (MO) and scanning electron microscopy coupled to a dispersive analysis system (SEM/EDS) were used in order to analyze the stratigraphic profile of mortar weathered samples collected from walls of the Bastion of San Pedro. According the results, the samples were formed by three substrata: an upper external layer in contact with the environment (100 to 300 µm), the other one is an inner layer with thickness around 100 to 400 µm. The last substrate was formed by the mortar matrix composed by elements such as C, O, Ca, Si and Al, that indicate their mineral origin. By the other hand, it is important to note that the upper layer contained higher proportion of C respect to the other layers. It is probably major consequence of biomass encrustation rather that atmospheric pollution according to the particular environmental conditions surrounding the building.

Magnetoelectric (ME) effects in bilayer composite cantilevers of magnetostrictive (MS) and piezoelectric (PE) materials on a substrate (Sub) are investigated theoretically for the FeCoBSi-AlN-Si system in open circuit mode and compared for different MS-PE-Sub layer thickness ratios and layer sequence choices. Static and resonant magnetic field excitations, the latter with resonance-enhanced cantilever oscillation, are investigated. Greatly differing behavior of the ME response with layer thicknesses is found for alternate layer sequences and excitation modes with the greatest resonant ME effect for the MS and PE layers on opposite sides of the substrate and the highest static effect for non-central substrates. The unexpected layer sequence systematics of the ME response are explained by the behaviour of the neutral (zero strain) plane in the strain coupled elastic layer stack.

Nitrogen-doped carbons nanoballs were synthesized from an organic liquid precursor (a mixture of benzene and pyrazine) by solution plasma process. After synthesis, they were further annealed at 700 and 900 °C under N2 atmosphere. The nitrogen-doped carbon nanoballs before and after thermal annealing process exhibit a similar morphological feature, and their diameters are in the range between 20 and 40 nm. With higher annealing temperature, the graphitization of the nitrogen-doped carbon nanoballs increases. For the electrocatalytic activity in an alkaline solution, the limiting current density and onset potential for the ORR activity can be significantly improved for the samples after thermal annealing at 900 °C. We anticipate that solution plasma process will be a viable alternative way for synthesizing heteroatom-doped carbon electrocatalysts for broad application in the field of fuel cells, metal-air batteries, and supercapacitors.

A novel method was developed for the preparation of arborescent (dendritic graft) polymers, by successive grafting reactions of linear chain segments using alkyne-azide “click” chemistry coupling. A linear polystyrene substrate was thus randomly functionalized with acetylene functionalities, by acetylation and further reaction with propargyl bromide in the presence of potassium hydroxide and 18-crown-6 in toluene. The anionic polymerization of styrene was achieved with 6-tert-butyldimethylsiloxy-hexyllithium to obtain polystyrene with a protected hydroxyl chain end. Deprotection of the hydroxyl group, followed by conversion into tosyl and azide functionalities yielded the material serving as side chains in the grafting reactions. Coupling of the azide-terminated side chains with the acetylene-functionalized substrate in the presence of a Cu(I) catalyst proceeded in up to 93% yield. Additional cycles of substrate functionalization and side chain coupling led to arborescent polymers of generations G1 and G2, with low polydispersity indices (Mw/Mn≈ 1.1), in 60-84% yield. These polymers are characterized by a very compact structure, and molecular weights increasing geometrically over successive generations. A similar methodology was also shown to work for the synthesis of arborescent polybutadiene systems, using azide-functionalized substrates and alkyne-terminated side chains. The coupling reaction proceeded in up to 76% yield under optimized conditions for these systems.

ZnO nanoparticles were prepared by a green electrochemical synthesis method applying low current densities followed by a thermal treatment. Sodium polystyrene sulphonate (PSS) was used as stabilizer in the electrolytic aqueous medium due to its biocompatibility and stability. The as-prepared nanocolloids were then annealed to improve their stability, and then converted via hydroxide species into stoichiometric oxide. Different calcination temperatures were studied. ZnO@PSS nanomaterials were deposited onto SiO2/Si substrates, in part in combination with an organic semiconductor layer to evaluate their influence on organic field effect transistors (OFETs). All nanomaterials and composite layers were characterized by morphological and spectroscopic techniques. Promising results regarding the use of ZnO@PSS in OFETs could be demonstrated.

A photoactivated ZnO nanomesh with precisely controlled dimensions and geometries is fabricated by using nanosphere lithography process. The nanomesh structures effectively increase the surface-to-volume ratio to improve the sensing response under the same testing gas. And the periodical nanostructures also increase the effective light path and lead to more efficient light activation for gas sensing. With the increase of the photoinduced oxygen ions by UV illumination, a distinguished sensing response is observed at room temperature. In the optimized case, the sensing response (△R/R0) of the ZnO nanomesh at the butanol concentration of 500 ppm is 97.5%, which is 4.54 times higher than the unpatterned one.

Uranium-plutonium mixed oxides incorporating high amounts of plutonium are considered for future nuclear reactors. For plutonium content higher than 20%, a phase separation occurs, depending on the temperature and on the oxygen stoichiometry. This phase separation phenomenon is still not precisely described, especially at high plutonium content. Here, using an original in situ fast X-ray diffraction device dedicated to radioactive materials, we evidenced a phase separation occurring during rapid cooling from 1773 K to room temperature at the rate of 0.05 and 2 K per second for a (U0.55Pu0.45)O2-x compound under a reducing atmosphere. The results show that the cooling rate does not impact the lattice parameters of the obtained phases at room temperature but their fraction. In addition to their obvious fundamental interest, these results are of utmost importance in the prospect of using uranium-plutonium mixed oxides with high plutonium content as nuclear fuels.

An epitaxial shell of cadmium sulphide is grown on lead sulphide quantum dots in order to reduce the concentration of surface defects. Thin solid films of these core/shell materials are found to have low carrier concentrations due to effective surface passivation which reduces the number of dangling bonds. In this paper PbS/CdS is used as a quasi-intrinsic layer in p-i-n photovoltaic devices where PbS acts as the p-layer and ZnO the n-layer. By studying different permutations of these layers and the degree of PbS p-type doping by annealing we optimise fill factor and open-circuit voltage.

The covalent functionalization of photosynthetic proteins with properly tailored organic molecular antennas represents a powerful approach to build a new generation of hybrid systems capable of exploiting solar energy. In this paper the strategy for the synthesis of the tailored aryleneethynylene organic fluorophore (AE) properly designed to act as light harvesting antenna is presented along with its successful bioconjugation to the photosynthetic reaction center RC from the bacterium Rhodobacter sphaeroides .

Carbon supported Pt-SnO2 electrocatalysts with different Sn/Pt molar ratios were prepared by an electron beam irradiation method. Dissolved gas conditions in the vials irradiated with electron beam were controlled to air or Ar. The results of the material analyses showed that both Pt and SnO2 were immobilized onto carbon support in all catalysts. Bubbling Ar to the precursor solution led to steady change of metal contents in response to the precursor concentrations. The ethanol oxidation activity plotted against Sn/Pt ratio behaved differently with dissolved gas condition of the vial. This difference is discussed with supposed existing state of SnO2 in connection with the reduction process of Pt and Sn.

Topographical features are known to influence the axonal outgrowth of neurons. Understanding what kinds of topographical features are most effective at growth cone guidance and how outgrowth responds to these structures is of great importance to the study of nerve regeneration. To this end we analyze axonal outgrowth on tilted nanorod substrates which have been shown to impart directional bias to neuron growth. We utilize the Atomic Force Microscope to characterize the surface features present on these substrates and how such features are influencing the axonal outgrowth. Additionally, using a model which considers the neuronal growth cone as an object influenced by an effective potential we determine an effective force imparted on the growth cone by the surface topography.

Carbon nanotubes (CNT) are expected to revolutionize a range of technologies because of their unique mechanical and electrical properties. Using nanotubes in structural materials holds significant promise due to their extremely high modulus and tensile strength, however their cost, production rate and integration into a fiber form severely limit the current structural application opportunities. The high cost of CNT is tied to their slow, batch synthesis using vapor phase, vacuum processes. We report the investigation of the formation of carbon nanotubes from a polymeric precursor using an electrospinning production process. Electrospinning generates nanofibers at velocities up to 10 m/s from a single nozzle without a vacuum requirement, with the potential to generate CNT appropriate from structural and electrical applications. Our CNT formation concept is based upon Reactive Empirical Bond order calculations that show carbon nanofibers have a thermodynamic preference for the cylindrical graphite conformation. Simulations suggest that for small diameter carbon fibers, less than about 60 nm, the single wall and multi wall nanotubes (SWNT and MWNT) phases are thermodynamically favored relative to an amorphous or planar graphitic nanofiber structure. We have developed a novel process using continuous electrospun polyacrylonitrile (PAN) nanofibers as precursors to continuous SWNT and MWNT. The process for converting PAN nanofibers to SWNT's and MWNT's follows the process for typical carbon fiber manufacture. The PAN nanofibers, of 10 to 100 nm in diameter, are crosslinked by heating in air and then decomposed to carbon via simple pyrolysis in inert atmosphere. The pyrolyzed carbon nanofibers are then annealed to form the more energetically favorable SWNT or MWNT phase, depending upon the precursor diameter. We will discuss the process and characterization data.

Spectroscopy technique is used for various applications, for example in archaeology, in order to analyze samples of floors, including material excavation sites. In this work the floor samples that were found in two rooms belonging to a house in a residential Hispanic area, at different stratigraphic levels corresponding to the classical period, as well as samples that were collected in two deposits of lime (El Refugio and El Llano) around the site mentioned were analyzed. The characterization of the samples of the archaeological site Chingú in Tula de Allende in the state of Hidalgo was carried out by using Scanning Electron Microscopy (SEM) to observe the morphology of the samples and Energy Dispersive X-ray Spectroscopy (EDS) to analyze the composition of cementitious material of the floors and natural material of lime deposits. Comparing these samples with other archaeological works of literature, the morphology and composition of manufactured floors will be discussed.

Coahuilite, a new variety of amber is described from the Late Cretaceous Olmos Formation (ca. 73 Ma.), Coahuila, north of México. This amber is totally distinct chemically and stratigraphically from the Miocene Chiapas amber (ca. 23-13 Ma.), Southern México, which according to mineral nomenclature is currently known as Simojovelite var. nov. Additionally, an emended description of Bacalite is proposed, based on the physicochemical analysis and geological record of a fossil resin recently recovery from the Late Cretaceous El Gallo Formation (ca. 73 Ma.), Baja California, northwestern México. The results are supported by characterization of such ambers using synchrotron-based Infrared (FTIR) microspectroscopy.